Optimizing Naphthalene Degradative Bacteria to Improve the Public Health

Background and Objectives: Polycyclic aromatic hydrocarbons (PAHs) are widely used and distributed. Naphthalene is one of them and it is available in crude oil (1.3%) and coal (11%). It is used as pesticide, hydronaphthalene which are harmful for the environment. The ability of microorganisms in each environment to degrade naphthalene depends on physicochemical conditions such as pH and salinity of that environment. Thus, it is important to figure out the important factors involved in the microorganism degradation abilities. Material and method: Samples were obtained from Persian Gulf, Caspian Sea, Zayandeh Rood, Karoun, and Isfehan wastewater treatment factory. Bushnell-Hass (BH) culture was used to grow them. Biochemical tests were applied for the identification of bacteria. Then, their ability to degrade Naphthalene was measured by using Gas Chromatography (GC) and UV-spectrophotometer. Finely pH, salinity, nitrogen source, and naphthalene concentration of the culture were optimized. Results and Conclusion: Six Gram negative bacteria were identified which could degrade the Naphthalene. All of them are salt tolerant and belong to Psedomonas genus. They were able to degrade the Naphthalene of the culture at rate as high as 90% within 6 days. The findings were that the optimum pH of all bacteria was 8.5 and their growths were inhibited in high concentration of NaCl. Nitrogen had no effect on degradation; also the optimum concentration of naphthalene of the maximum growth was 2000 ppm. Strain SA58 (which was isolated from sea water) and strain SA86 (which was isolated from fresh water) had highest naphthalene degradation activity and this makes them good candidates for removing naphthalene from environments. This would lead to reduce this hazardous material from the environment, which consequently reduces the risk of diseases associated with it.